Mobile devices such as cellular telephones, PDAs, etc. are proliferating like never before. Almost everyone has some sort of mobile device, and some people have multiple devices. Users can access several different networks using a single mobile device, and can access voice, text, and multimedia data from other network entities such as servers and other mobile devices. Further, mobile device complexity is increasing, with more and more advanced and power efficient processors, display interfaces, and applications to provide a user experience like never before. Such devices include, for instance, the iPhone®, iPad®, Droid®, and other PDAs I netbooks.
These mobile devices additionally include Global Positioning System (GPS) receivers, which provides for a host of location-based services (LBS). Location estimation of mobile devices, in for instance a 3G UMTS system, is important for obtaining location tagged network failure data for system optimization, location based services, 911 services, and a variety of other location enhanced applications. Although GPS receivers enable precise location determinations, GPS receivers do not always receive satellite signals. This problem is highlighted in several situations, for instance in buildings, basements, or generally where the signal from a satellite is blocked for some reason. Estimating accurate (sub 100 m median accuracy) location of 3G mobile devices today typically consists of relying on Assisted (AGPS) devices to achieve the desired accuracy. The problem however, is that mobiles can only report AGPS location estimates if they actually see enough satellites, which essentially limits AGPS locates to mobiles which are “outdoors, in-vehicles or by windows”. By some estimates this means that between 30-50% of mobile locates are not able to return AGPS location information.
Commonly owned and assigned patent application Ser. No. 12/712,424, now issued as U.S. Pat. No. 8,224,349, on Jul. 17, 2012 (the NELOS application), describes methods to determine a location of non-GPS mobile devices using network probes that measure timing offsets for base stations pairs and forwards these timing offsets to the mobile device to assist in a location determination. However, this relies on functionality on the network, which may not always be available to the mobile device. Further this does not allow for locating devices serviced by base station pairs that are not operated by the same network operator that owns the network servers.
Consequently, what is needed is a technique to determine a location of a non-GPS mobile device to a precise degree without relying on unnecessary intelligence on the network.